1. Field of the Invention
The present invention relates to a wireless communication unit, and more particularly to a portable transmitter that transmits electromagnetic waves via an antenna of the transmitter powered by a button type battery.
2. Description of the Related Art
Conventionally, a remote key-less system which opens and closes vehicle-doors and starts the engine of the vehicle is known. In the remote key-less system, electromagnetic waves are transmitted/received between user's transmitter device and an on-vehicle unit to verify whether or not the transmitter corresponds to the on-vehicle unit.
In such a remote key-less system, to shrink the size of the transmitter, for example, a Japanese Patent Application Laid-Open No. 2007-187519 discloses a watch having a structure accommodating a button type battery, an antenna laminated on a board together with the button type battery.
In the above-described structure, the transmitter supports the button type battery by using a battery frame that supports the battery. The board having the antenna and the battery frame are fixed to a watch-body by screws and the battery is inserted to the battery frame. Then, a cap portion of a back surface of the watch is fixed to the watch-body by the screws as well. Therefore, it is considered that a problem arises in the assembly step to manufacture this structure. Moreover, the battery frame needs to occupy a space in the structure. Hence, it is considered that downsizing cannot be performed easily.